Along with the development of the network architecture, various network open technologies appear based on the requirements of the network flattening and the rapid service deployment by the network operator. The packet processing is separated from the network devices, such as a router or switch, and operated in a special control server. Such technologies enable the network to be easier to be planned and managed, and opened based on the current network pattern.
The openflow technology converts a packet forwarding process controlled by a switch or router originally into a technology to be controlled by an openflow switch (or router) and a control server together, thereby achieving the separation of the data forwarding and the routing control. The process is mainly described as follows: the control server establishes a connection with the control layer of the switch (or router) through a Transmission Control Protocol (TCP) or Secure Sockets Layer (SSL); when receiving a data packet, the forwarding layer of the switch (or router) transmits the data packet to a secure channel of the control layer; the secure channel performs the TCP and openflow encapsulation of the packet (for the convenience of description, hereinafter the encapsulated data packet is referred to as an encapsulated packet) and transmits the forwarded packet to the control server; the control server parses the encapsulated packet, converts original data and port information in the encapsulated packet into flow table information and returns the flow table information to the control layer of the switch (or router) by a TCP channel; and then the control layer of the switch (or router) sends the flow table information to the flow table of the switch (or router).
Although the above method can achieve the separation of the data forwarding and the routing control, the openflow establishes the connection based on the TCP/SSL and its performance is completely restricted by the communication capacity between the control layer and the forwarding layer of the switch (or router). However, generally, the communication bandwidth between the control layer and the forwarding layer of the switch (or router) is very small, and it is merely suitable for control layer processing, such as network protocol packets including Open Shortest Path First (OSPF) protocol, Multi-Protocol Label Switching (MPLS) protocol, Border Gateway Protocol (BGP), etc. It is clear that the openflow technology has a performance bottleneck.